Plant thinning machine and method of thinning plants



Dec. 19, 1967 GARRETT 3,358,775

PLANT THINNING MACHINE AND METHOD OF THINNING PLANTS Origmal Filed April22, 1965 4 Sheets-Sheet l INVENTOR. P06 5. 642F577 R. E. GARRETT PLANTTHINNING MACHINE AND METHOD Dec. 19, 1967 OF THINNING PLANTS OriglnalFiled April 22, 1965 4 Sheets-Sheet 2 TOR.

INVEN Posse 642F577 OMA WM i r ew'fi Dec. 19, 1967 R. E. GARRETT3,358,775

PLANT THINNING MACHINE AND METHOD OF THINNING PLANTS Origmal Filed April22, 1965 4 Sheets-Sheet 5 INVENTOR.

Dec. 19, 1967 R. E. GARRETT 3,358,775

PLANT THINNING MACHINE AND METHOD OF THINNING PLANTS Origmal Filed April22, 1965 4 Sheets-Sheet 4,-

/ INVENTOR.

Pam-e5. 6422577 4% aw/J United States Patent C) 3,358,775 PLANT THINNINGMACHINE AND METHOD OF THINNING PLANTS Roger E. Garrett, Davis, Calif.,assignor to The Regents of The University of California, Berkeley,Calif.

Continuation of application Ser. No. 449,963, Apr. 22,

1965. This application Nov. 22, 1966, Ser. No. 596,344

4 Claims. (Cl. 172-6) This is a continuation of application Serial No.449,963, filed Apr. 22, 1965, and now abandoned.

My invention relates primarily, although not exclusively, toagricultural machinery and is particularly concerned with a mechanismand method by means of which the plants growing in a field afterplanting are reduced in number and spacing to a close approximation of adesired pattern.

In the cultivation of many plants; for example, lettuce and the like, itis customary to level the land quite accurately, particularly forirrigation, and to leave the land cultivated in furrows evenly spacedapart on opposite sides of parallel ridges. Lettuce seed is planted inthe ridges in rows or lines generally straight and spaced apart apredetermined distance from the adjacent rows and with the furrows inbetween. Because of uncertainities in the emergence of seed, it iscustomary to plant in the row from twelve to fifteen times as many seedas would be requisite for the desired plants in proper spacedrelationship if the emergence were one hundred percent successful. Whenthe young plants then appear in the rows from those seeds that haveemerged, it is customary to thin them by eliminating the plantsintervening between those specimens which are to be permitted to grow tomaturity. The retained plants are usually spaced apart an arbitrarydistance; for example, one foot apart along the row or line.

Thinning has heretofore been practiced by manual means. This require agreat deal of labor and particularly labor of a sort now diflicult toget. There is, consequently, a demand for an improved mechanism andmethod for arriving at properly spaced, maturing plants and foreliminating intervening plants.

Machines for this purpose have heretofore been proposed. Many of themwork by a technique of arbitrarily eliminating blocks of plants betweengeometrically predetermined sites. The difliculty is that sometimes aspecimen does not actually occur at the expected geometrical site and anadjacent plant is removed which otherwise could be permitted to grow tomaturity as a substitute. There has, consequently, been developedmechanism for sensing the occurrence of a plant in the row at anylocation and for then eliminating the adjacent plants. A difficulty hasarisen, however, in that the sensing mechanisms employed if suflicientlysensitive are likewise upset by the general vibration and motion of themachine, so that signals are generated when none should properly begiven, and great practical difiiculties have arisen.

Other devices of this sort rely upon the use of electric eyes andcomparable optical sensing devices. These are reasonably effective whenthey are clean, but normal operating conditions in the field,particularly dust, tend quickly to interrupt the satisfactory operationof the optical system. There is usually considerable unreliabilityconnected with optical selecting means.

It is therefore an object of the invention to provide a plant thinningmachine and method which are effective to sense the presence of a plantin a row and for removing adjacent blocks of plants, and which are notdisturbed by random motion and vibration and are not adversely affectedby dust or comparable deleterious ambient conditions.

Another object of the invention is to provide a plant the wheels byjournals 3,358,775 Patented Dec. 19, 1967 thinning machine which can beutilized in connection with rows of plants as ordinarily planted andwhich is effective to remove a block of plants only when such block isadjacent a plant specimen that is to be preserved.

Another object of the invention is to provide a plant thinning machinewhich acts quickly and accurately to detect an appropriate specimenplant and to remove the adjacent undesirable plants.

Another object of the invention is to provide a plant thinning machinewhich depends for its operation upon the characteristics of a specimenplant itself.

Another object of the invention is to provide a plant thinning methodwhich utilizes the plant itself as part of the selection step. I

Another object of the invention is to provide an improved plant thinningmachine.

Other objects together with the foregoing are attained in the embodimentof the invention and in the practice of the method thereof described inthe accompanying description, the device being illustrated in theaccompanying drawings, in which:

FIGURE 1 is a plan of one form of plant thinning machine constructedpursuant to the invention, the machine being shown in action in thefield;

FIGURE 2 is a cross section, the planes of which are indicated by thelines 2-2 of FIGURE 1;

FIGURE 3 is a plan of a modified form of device pursuant to theinvention;

FIGURE 4 is a cross section through a portion of the device of FIGURE 3,the plane of section being indicated by the line 4-4 of FIGURE 3;

FIGURE 5 is a fragmentary view showing in side elevation one form ofplant removing structure; and

FIGURE 6 is a schematic diagram showing the electrical circuitryemployed in connection with the structure.

While the plant thinning machine pursuant to the invention can beembodied in a number of different forms, it has successfully beenoperated in both of the forms shown herein. As shown in FIGURES 1 and 2,the structure is for use on the ground 6, which has previously beenprepared to provide ridges 7 and intervening furrows 8. In each ridgethere is provided a row 9 of plants. Usually two parallel lines or rowsare planted, but for simplicity herein, but one line or row is shownlocated on the longitudinal center line of the ridge. The plants are ofany sort, but for convenience are illustrated as lettuce. Eventually theplants must be spaced more or less evenly a large distance apart.Initially, enough seeds are planted so that the young plants are veryclose together, although some seeds may not grow at all, resulting inrandom gaps.

Designated to operate on the ground 6 is a carriage 11 including a metalframe 12 made up of a number of structural shapes supported on a pair offront wheels 13 and 14 and a rearward wheel 15. Usually the Wheels 13,14 and'15 are rubber tired. The frame is connected to 16 and 17 carryingthe wheel axles 18. The carriage 11 is advanced in the direction of thearrow 21 in FIGURE 1 by any suitable propulsion mechanism represented.by draft beams 22. If desired, the carriage 11 can actually beconstituted by a tool bar or comparable part of a tractor.

Adjacent its rearward portion, the frame 12 is provided with asupporting plate 23 overlying the rearmost wheel 15 and supporting anoperating shaft 24 carried in bearings 26 and 27 and disposed in ahorizontal plane. The shaft axis is at an angle to the line of the row 9and to the direction of advance 21. The shaft 24 carries a rotary disc28 of a diameter so that the rim of the disc comes close to or evenslightly below the upper surface of the ridge 7. The disc for a portionof its periphery is interrupted to provide a window 29 of rectangularconfigura tion extending in from the rim of the wheel and of 3snflicient area to pass easily the largest size specimen with which thedevice is to work. The disc 28 when not rotating is locked or held in afull cycle position so that the window 23 is in a central position, asshown in FIGURE 2, and passes the plants freely.

The orientation of the disc is controlled by connecting a sprocket 3-1on the shaft 24 by means of a chain 32 to a sprocket 33 on a clutchshaft 34. The clutch shaft extends from a housing 35 encasing a singlecycle clutch 36. This clutch is not illustrated in detail, but is astandard commercial item. It has the characteristic of remaining lockedin a set position until it is momentarily energized. Upon energization,the clutch is eifective to drive the shaft 34 through exactly onerevolution and then to lock the shaft in its full cycle position untilanother energization is received.

The single cycle clutch is mechanically driven. Extending from thehousing 35 is a clutch drive shaft 37 connected through appropriatebevel gears (not shown) located in a housing 38 on the plate 23 to adrive shaft 39. A belt 41 is in engagement with a pulley 42 on the driveshaft 39 and is also in engagement with a drive pulley 43 on the axle 18of the rear wheel 15. As the frame advances and the wheel 15 isrevolved, the motion is transmitted by the belt 41 and through the bevelgears and the shaft 37 to the single cycle clutch.

As the carriage advances along the row 9, the disc 28 remains fixed inits full cycle position until such time as an impulse is received toactuate the single cycle clutch. Thereupon the disc 28 revolves throughone rotation as the machine advances. When the disc returns to itsoriginal location, it is again locked in full cycle position, pendingthe receipt of a further impulse.

lursuant to the invention, particular means are provided for sending anappropriate actuating impulse to the single cycle clutch 36.

Connected to the frame 12 is a housing 44 containing certain electricalequipment and on which is fastened an insulating support 46 engaging theinsulating enclosure 47 of a probe 48. The probe is an electricconductor 48 located within the casing 47 except that its end iscompletely exposed. The exposed end of the probe is disposed a shortdistance above the surface of the ridge 7 and is located so as to spanthe row 9 as the device advances.

The operation of the probe is in part dependent upon the height of aplant. If a plant is not sutiiciently far above the ridge 7 as to becontacted by the advancing probe 48, there is no signal. If the plant issufficiently high, when the advancing probe 48 comes into contact withit, an electrical signal is given. This is preferably accomplished bycompleting an electrical circuit through the plant acting as anelectrical conductor. The circuit is traced through the ground 6 and themachine frame 12. The tires 13, 14 and 15 are usually non-conductingrubber, insulating the frame from the ground. A metal disc 49 is mountedon the axle 18 of the rear wheel and digs into and forms an electricalcontact with the ground and is connected to the other metallic parts ofthe frame.

The electronic circuitry within the housing 44 is such that when theprobe comes even lightly into contact with a plant, an impulse isprovided for the single cycle clutch 36. It is not necessary to keep theprobe particularly clean and free of dust and the like, nor is machinevibration important since the least abutment of the plant with the probeis suflicient to cause energization. It is true that an unwanted plantsuch as a weed can also actuate the probe, but in the usual case thewanted plants extend above the ridge farther than weeds do, so that byappropriate vertical adjustment of the probe and by utilizing themechanism at the right time in thegrowing season, it is possible toeliminate virtually all extraneous weed influence.

It is also true that a clod or the like in the path of the probe andcontacted by the probe will also trigger the single cycle clutch. In theusual field cultivation, however, the top of the ridge 7 is relativelysmooth and devoid of clods so that it is unusual for an erranttriggering to occur.

When triggered by a plant, the single cycle clutch 36 revolves the disc28 through one turn. As soon as the window 29 has cleared the top of theridge 7, the periphery of the disc acts virtually as a plow and removesthe up standing plants from the ridge ahead of it and shunts such plantsto one side into the furrow 8. The disc continues to remove plants asthe machine advances until such time as the window 29 is virtually backin its full cycle position. The next large plant passes through thewindow and itself then contacts the probe to actuate the clutch. In thisfashion and with a steady advance of the machine, the disc upon eachactuation is effective to remove plants from a predetermined distancealong the ridge. At the end of that distance, should there be noupstanding plant, the machine will continue until such time as anupstanding plant passes through the window 29 and does come into contactwith the probe, whereupon the removal operation repeats.

If there are plants in the row of insuflicient height to be engaged bythe probe 48, these unwanted smaller plants are removed by a trailingblade 51 attached to the periphery of the disc 28. The blade is behindthe window and is sufiiciently spaced behind the disc to afford adequateroom for a plant of full size. The blade acts as a scraper to cut 01?plants in its path but is rotated away from a full-size plant that hascontacted the probe.

In a modified form of the invention shown in FIG- URES 3 and 4, thecarriage and frame are substantially as previously described. There isattached to the frame 61 a longitudinally extending shaft 62 carried inbearings 63 and 64 and effective to oscillate about a longitudinal axissubstantially parallel with the plant row 66. Mounted on the shaft 62and depending therefrom is a radially adjustable blade 67 having abranched lower end 68. The blade is constituted either of a singleportion or, as shown particularly in FIGURE 5, is constituted of a pairof portions 69 and 71 spaced apart in the direction of ad= vance of themechanism to leave a gap.

Extending from the shaft 62 is a crank arm 72 pivotally' joined througha link 73 to the piston rod 74 of a pneu matic jack 76 including acylinder 77. The motion of the piston rod 74 is controlled by an airvalve 78 on the jack 76 in turn controlled by a solenoid 79.

Mounted on the frame 61 in a position trailing the blade 67 is a probe81 comparable to the previously described probe. An electricallyconducting central member is surrounded by an insulating cover 82,except for a bare end, and is mounted on the frame as before. The probeis adjustable and is connected to electronic circuitry included in ahousing 84 mounted on the frame. In this in stance, when the probe 81comes into physical and electrical contact with a plant 85, a circuit iscompleted from the probe through the ground, then through a groundingplate 86 to the frame of the machine to which the probe circuitry isconnected. When the circuit is closed, the solenoid 79 is actuated bythe electrical impulse and the air jack 76 is effective to reciprocatethe blade 67 in either of two modes.

In one mode, the blade is reciprocated from right to left, in FIGURE 4,from the full line position into the dotted line position. Thistransverse motion sweeps out all of the plants or a block of plantsimmediately ahead of the plant 85 that contacted the probe 81. Followingthis, the knife 67 sweeps back from left to right to its initialposition and stops. In the other mode of operation, the blade 67 sweepsfrom the right-hand position to the left-hand position and then stops.The next impulse then causes the blade to sweep from the left-handposition back to the right-hand position and stop. If all of the trash,removed plants and earth, is to be in one furrow, the

blade 67 makes a complete excursion in both directions. If trash is tobe deposited in both furrows, then the blade makes an excursion in onlyone direction for each impulse.

If the form of blade particularly shown in FIGURE 5 is utilized, thenthe blade not only removes a block of plants in advanceof the selectedplant, but also the blade sweeps or re-sweeps the area in the row behindthe selected plant. There may be some overlapping of the swept areas,but there. is asurance that a predetermined free area is afforded bothahead of and behind the selected plant. a

In both forms of the invention, the electronic circuitry utilized issubstantially as shown in FIGURE 6. The frame of the machine operates atground potential, as indicated by the frame ground 101. A source ofcurrent at a relatively high voltage; for example, one hundred ten voltalternating current, is provided across a pair of conductors 102 and103. The conductor 103 extends to the solenoid 79 which actuates the airvalve 78. A lead 104 connects the solenoid 79 to a selector switch 105which has two optional positions. In the position shown, the switch 105connects through a conductor and a switch 106 to the conductor 102. Whenthe switch 106 is closed, the solenoid is energized to operate the valve78 so that the jack completes an outstroke and an instroke. In otherposition, the switch 105 connects through a conductor 107 and a switch108 as well as a conductor 109 to the conductor 102. When the switch 108is first actuated, it operates the valve 78 so that the jack completesan outstroke. When the switch 108 is next actuated, it operates thevalve 78 so that the jack completes an instroke. Thus, the switch 105controls the two modes of operation of the blade portions 69 and 71.When the disc 28 is used, the solenoid 79 is arranged to operate thesingle cycle clutch 36, and the switch 105 and the switch 108 areomitted.

The switch 106 is operated by a solenoid 110 while the switch 108 isoperated by a solenoid 111 connected in parallel with the solenoid 110in an electrical circuit operating with direct current at a low voltageand entirely isolated from the high voltage circuitry. A battery 112 isconnected by a conductor 113 to ground 6. This is an actual earthconnection through the disc 49 or the plate 86. The other side of thebattery is joined by a conductor 114 to one side of a switch 115. Theother side of the switch 115 is connected by a lead 116 to one side ofthe two solenoids 110 and 111. The other side of the solenoids 110' and111 is joined by a conductor 117 to the cathode of a silicon controlledrectifier 118, the anode of which is connected to ground by a conductor119.

The probe 48 (or 81) connects through a lead 120 to a junction point 121from which a conductor 122 containing a variable resistor 123 and afixed resistor 124 extends to a junction with the conductor 114. Alsofrom the junction point 121 a lead 125 connects to the gate of a fieldeffect transistor 126, the drain of which is joined by a lead 127 to theconductor 119 and the source of which is connected to a lead 128extending to a Zener diode 129. A resistor 130 is connected to the lead128 and to the conductor 114. A diode 131 is connected in the oppositedirection to the Zener diode by a connector 132 and is connected to theemitter of the transistor 118 by a conductor 133. A variable resistor134 is connected to the conductors 133 and 114.

From the conductor 117 a lead 135 branches to connect respectively to avariable resistor 136 and to a diode 137, both connected to a lead 138that in turn branches to connect to one side of a capacitor 139 and toone end of a switch coil 140. A connector 141 joins both the other sideof the capacitor 139 and the other end of the switch coil 140 through avariable resistor 142 to the lead 116.

This circuit is stable and quiescent until a plant or similar objectcontacts the probe 48 (or 81). Thereupon energy is supplied to thesolenoids 110 and 111 to actuate the switches 106 and 108 and to producewhichever mode of air jack operation is selected by the switch 105.Energy is also supplied to the switch coil 140 so that shortly after thecoils 110 and 111 have acted the switch 115 is opened and the circuit isrestored to quiescence. The time delay is governed by the resistors 136and 142 so that 6 an inadvertent contact with the probe too soon afteran actuation thereof is ineffective.

The sensitivity of the electronic circuitry varies with the values ofthe circuit components. It has been found in practice that an extremelysensitive response can be had to the presence of a plant against theprobe. Yet this same sensitivity does not in any Wise cause an actuationof the solenoid air valve or of the single cycle clutch because ofvibration or motion or shaking of the mounting machine. In fact, the useof the electrical properties of the plant is effective to precludeoperation of the structure by any normally encountered disturbingforces. It has also been found in practice that the sensitivity of thearrangement is such as not to be unusually affected by the short-termvariations in moisture content of the plant or in moisture content ofthe ground, the average'agricultural conditions or the normal variationtherein all being sufiicient for operation of the structure.

The sensitivity of the circuitry can be made such that the returncurrent through the ground to the ground conductor 101 may beexceedingly slight, in fact so slight as to indicate that the factorwhich unbalances the circuit and causes the triggering action is not somuch the conduct of electricity through the plant, but in many instancesis merely the body capacity of the plant itself. That is to say, anabrupt change in capacity made manifest in the lead 120 is sufiicient tocause triggering of the circuitry and operation of the structure. Infact, under some conditions, the ground connection 101 can be omittedand the contact of a plant with the probe 48 (or 81) will trigger theoperation of the solenoids and 111.

The electronic circuitry has its own battery 112 and is electricallyisolated from the usual electrical equipment found on a draft tractor orcomparable mechanism since stray currents in the framework may triggerthe mechanism when triggering is not wanted. By varying the sensitivityof the electronic circuitry, either the return flow current through theplant and the ground or the capacity effect of the plant when contactedcan be used separately or can be combined.

What is claimed is:

1. A plant thinning machine for use With a row of plants growing in theground comprising a frame adapted to be advanced over said ground alongsaid row, a shaft, means for mounting said shaft on said frame forlimited oscillation about an axis extending lengthwise of said row andsituated directly above said row of plants, a blade mounted on saidshaft and disposed in a plane containing said axis, said blade having alength substantially equal to the length of a block of said plants to beremoved from said row and having a radial dimension terminatingsubstantially at said ground in the central position of oscillation ofsaid blade in a position to dislodge some of said ground into thevicinity of said plants as said blade oscillates, an electricallyconducting probe, means for mounting said probe on said frame to extendtransversely of said row in a location slightly above the ground andjust to the rear of said blade in a position in the path of some of saidground dislodged by said blade, means for oscillating said shaft toswing said blade from a first position on one side of said row throughsaid row to a second similar position on the other side of said row, anelectrical circuit including said probe and a return portion and adaptedto be completed through said plant and said return portion by contact ofsaid probe with a particular plant in said row, and means responsivesolely and immediately to completion thereof to operate said oscillatingmeans to make one swing of said blade, beginning at said first positionand ending at said second position just ahead of said particular plant.

2. A device as in claim 1 in which control means are provided forselectively conditioning said circuit to swing said blade from saidfirst position to said second position in response to one contact ofsaid probe with a plant and then swing said blade from said secondposition to said first position in response to a subsequent contact ofsaid probe with another plant or for swinging said blade from said firstposition to said second position and immediately back to said firstposition in response to each contact of said probe with a plant.

3. A device as in claim 1 in which a second blade substantially aduplicate of said first blade is mounted on said shaft coplanar with andrearwardly of said first blade, said first blade and said second bladebeing spaced axially apart to accommodate said probe and one of saidplants between them.

4. A device as in claim 1 in which means are provided for retaining saidblade either in said first position or said second position except whensaid oscillating means is operated in response to contact of said probewith a plant.

References Cited UNITED STATES PATENTS 225,890 3/1880 Sustaire 172-73 XMarable -2 17273 Hann 172-6 Bowman 172-5 Rhode 1726 Boncompain.

Myer 172-6 Hubalek et al. 1726 Cracknell et a1. 172-6 Miller ..o t 1726Ferte 172-6 FOREIGN PATENTS Germany.

ROBERT E. BAGWILL, Primary Examiner.

1. A PLANT THINNING MACHINE FOR USE WITH A ROW OF PLANTS GROWING IN THEGROUND COMPRISING A FRAME ADAPTED TO BE ADVANCED OVER SAID GROUND ALONGSAID ROW, A SHAFT, MEANS FOR MOUNTING SAID SHAFT ON SAID FRAME FORLIMITED OSCILLATION ABOUT AN AXIS EXTENDING LENGTHWISE OF SAID ROW ANDSITUATED DIRECTLY ABOVE SAID ROW OF PLANTS, A BLADE MOUNTED ON SAIDSHAFT AND DISPOSED IN A PLANE CONTAINING SAID AXIS, SAID BLADE HAVING ALENGTH SUBSTANTIALLY EQUAL TO THE LENGTH OF A BLOCK OF SAID PLANTS TO BEREMOVED FROM SAID ROW AND HAVING A RADIAL DIMENSION TERMINATINGSUBSTANTIALLY AT SAID GROUND IN THE CENTRAL POSITION OF OSCILLATION OFSAID BLADE IN A POSITION TO DISLODGE SOME OF SAID GROUND INTO THEVICINITY OF SAID PLANTS AS SAID BLADE OSCILLATES, AN ELECTRICALLYCONDUCTING PROBE, MEANS FOR MOUNTING SAID PROBE ON SAID FRAME TO EXTENDTRANSVERSELY OF SAID ROW IN A LOCATION SLIGHTLY ABOVE THE GROUND ANDJUST TO THE REAR OF SAID BLADE IN A POSITION IN THE PATH OF SOME OF SAIDGROUND DISLODGED BY SAID BLADE, MEANS FOR OSCILLATING SAID SHAFT TOSWING SAID BLADE FROM A FIRST POSITION ON ONE SIDE OF SAID ROW THROUGHSAID ROW TO A SECOND SIMILAR POSITION ON THE OTHER SIDE OF SAID ROW, ANELECTRICAL CIRCUIT INCLUDING SAID PROBE AND A RETURN PORTION AND ADAPTEDTO BE COMPLETED THROUGH SAID PLANT AND SAID RETURN PORTION BY CONTACT OFSAID PROBE WITH A PARTICULAR PLANT IN SAID ROW, AND MEANS RESPONSIVESOLELY AND IMMEDIATLEY TO COMPLETION THEREOF TO OPERATE SAID OSCILLATINGMEANS TO MAKE ONE SWING OF SAID BLADE BEGINNING AT SAID FIRST POSITIONAND ENDING AT SAID SECOND POSITION JUST AHEAD OF SAID PARTICULAR PLANT.